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Analysis of One-Minute Potentially Available Fluoride from Dentifrice



Clifton Carey, Erin Holahan


Previous reports found that some fluoride containing dentifrices do not release effective concentrations of fluoride during brushing. Failure to release fluoride can be due to dentifrice matrix components that interfere with the solubilization of the fluoride salts during brushing. A new generation of dentifrices have the capability to precipitate fluoride salts during tooth brushing. Therefore, a method that assesses the potentially available fluoride during the 1-minute brushing is needed. To meet this need, we developed a new filter- paper absorption method to assess the 1-min bioavailable fluoride concentration. This method utilizes coiled filter paper which rapidly absorbs the aqueous phase of the dentifrice slurry followed by centrifugation to recover that fluid for fluoride measurement via F-ISE. The analytical method was used to successfully determine the total fluoride and 1-min bioavailable fluoride in eight dentifrice products containing NaF, monofluorophosphate (MFP), SnF2, or NaF + amorphous calcium phosphate (ACP). The results found that some of the dentifrices tested had significantly lower potentially available fluoride than the total fluoride. For an aged MFP- containing sample there was significant reduction in the bioavailable fluoride compared to MFP products that were not aged. Other than the aged MFP and the SnF2-containing samples the bioavailable fluoride for all products tested had at least 80 % of the label fluoride concentration, meeting current U.S. FDA requirements [U.S. FDA, 1995]. The filter paper absorption method yielded reproducible results for the products tested with MFP samples showing the largest variations.
Journal of Research (NIST JRES) - 119.025
Report Number


Analysis, available fluoride, dentifrice, fluoride, Fluoride Ion-Selective Electrode (F-ISE)


Carey, C. and Holahan, E. (2014), Analysis of One-Minute Potentially Available Fluoride from Dentifrice, Journal of Research (NIST JRES), National Institute of Standards and Technology, Gaithersburg, MD, [online], (Accessed April 17, 2024)
Created December 4, 2014, Updated November 10, 2018